1. Field of the Invention
The present invention relates to coating and developing treatment method and system for a substrate.
2. Description of the Related Art
In photolithography of the process of fabricating a semiconductor device, for example, resist coating treatment for forming a resist film on the surface of a wafer, developing treatment for developing the wafer after pattern exposure, heat treatment and cooling treatment performed before the coating treatment, before and after exposure processing, and after the developing treatment, and the like are performed. Such treatment and processing are performed in treatment units provided individually, and these treatment units are unified as a coating and developing treatment system so as to continuously perform the aforesaid successive treatment and processing. The exposure treatment of a pattern is usually performed in an aligner disposed adjacent to the coating and developing treatment system.
When the wafer is treated in this coating and developing treatment system, air cleaned by an air cleaner or the like, for example, is supplied as down-flowing air into the coating and developing treatment system in order to prevent impurities from adhering to the wafer, while an atmosphere in the coating and developing treatment system is exhausted, whereby the wafer can be treated in a clean condition.
In recent years, however, exposure technology in which a beam with a shorter wavelength (for example, 157 nm) is used is being developed to form a finer and more precise circuit pattern. When the beam with the short wavelength is used, there is a fear that even impurities at molecular level such as oxygen, ozone, and water vapor which have been insignificant so far exert a bad influence on exposure processing, whereby a precise circuit pattern is not formed.
Hence, when at least the wafer is subjected to exposure processing, it is required that no impurities such as oxygen adhere onto the wafer. If only clean air is supplied as in prior arts, the adhesion of impurities onto the wafer can not be suppressed effectively since impurities such as oxygen are contained in the air, and moreover impurities adhering onto the wafer can not be removed.